This application claims the priority benefit of Taiwan application serial No. 88107474, filed May 7, 1999, the full disclosure of which is incorporated herein by reference.
1. Field of the Invention
This invention relates to means for setting options to a computer chipset, and more particularly, to a multi-option setting device for a peripheral control chipset, which is designed for use in association with a connecting pin of the chipset for the purpose of allowing user-selection from more than two setting options to set the chipset to perform one of more than two I/O functions through the associated connecting pin.
2. Description of Related Art
An IC chip is typically provided with a plurality of pins that can be externally connected for input/output of various signals. Some types of chips come with pins that can be selectively set to perform different I/O functions. For example, the South Bridge chipset comes with an IDE2/Audio pin which can be selectively set to be used either for IDE2 I/O function or for audio I/O function. More specifically, when the IDE2/Audio pin is set to a low-voltage logic stage (typically the ground voltage, which is below 0.7 V) at power-on, it is set to be used for IDE2 I/O function; and whereas, when set to a high-voltage logic state (typically above 2.8 V) at power-on, it is set to be used for audio I/O function. These two different settings are depicted in the following with reference to FIGS. 1 and 2, respectively.
FIG. 1 is a schematic diagram of a South Bridge chipset 10 whose IDE2/Audio pin is specifically set to be used for IDE2 I/O function. As shown, the IDE2/Audio pin is internally connected to a control unit 12 and externally connected via a pull-down resistor R1 to the ground. At power-on, the IDE2/Audio pin will take on the ground voltage via the pull-down resistor R1, thereby being set to a low-voltage logic stage. This condition then causes the control unit 12 to set the IDE2/Audio pin to be used for IDE2 I/O function.
FIG. 2 is a schematic diagram of another South Bridge chipset 20 whose IDE2/Audio pin is specifically set to be used for audio I/O function. As shown, the IDE2/Audio pin is internally connected to a control unit 22 and externally connected via a pull-up resistor R2 to a system voltage VCC representative of a high-voltage logic state. At power-on, the IDE2/Audio pin will take on the system voltage VCC via the pull-up resistor R2, thereby being set to a high-voltage logic state. This condition then causes the control unit 22 to set the IDE2/Audio pin to be used for audio I/O function.
In addition to the schemes shown in FIGS. 1 and 2, the selective setting of the IDE2/Audio pin between IDE2 I/O function and audio I/O function can be carried out by means of the BIOS (Basic Input-Output System) of the PC. This scheme, however, requires the PC to be restarted each time the setting is changed so as to allow the new setting to take effect, which is quite inconvenient for the user to do so.
Therefore, the prior art only allows the user to selectively use the IDE2/Audio pin of a South Bridge chipset for one of two I/O functions. There exists, however, a need for a multi-option setting device that allows one single connecting pin to be selectively used for more than two I/O purposes, for example three I/O functions including IDE2 I/O function, audio I/O function, and GPIO (General Purpose Input/Output) I/O function.
Moreover, some customers may demand the elimination of certain I/O functions, such as the IDE2 I/O function. In this case, the IDE2/Audio pin would not be required to be set for IDE2 I/O function.
It is therefore an objective of this invention to provide a multi-option setting device for a chipset, which allows the user to select from more than two setting options for the purpose of setting the chipset to perform a selected I/O function through the same connecting pin of the chipset.
In accordance with the foregoing and other objectives of this invention, a multi-option setting device for chipset is provided. The multi-option setting device is designed for use in association with a connecting pin of the chipset for the purpose of allowing user-selection from more than two setting options to set the chipset to perform one of more than two I/O functions through the associated connecting pin. The multi-option setting device comprises: (a) voltage setting means for generating a user-specified input voltage whose value corresponds to one of a plurality of I/O functions that can be performed by the chipset through the associated connecting pin, with each I/O function corresponding to a prespecified range of voltage levels; (b) a voltage comparison circuit for comparing the user-specified input voltage against a plurality of preset reference voltages to thereby generate an output signal indicative of which prespecified voltage range the user-specified input voltage lies; (c) a latch circuit for latching the output signal of the voltage comparison circuit; and (d) a control unit, in response to the latched output signal from the latch circuit, for setting the connecting pin to the user-selected I/O function corresponding to the user-specified input voltage.
The voltage comparison circuit includes: a plurality of analog comparators, each having a positive input end connected to receive the user-specified input voltage and a negative input end connected to receive one of the plurality of reference voltages; each analog comparator generating a first logic signal when the user-specified input voltage is greater in level than the reference voltage connected thereto, and a second logic signal when the user-specified input voltage is lower in level than the reference voltage connected thereto.
The foregoing multi-option setting device of the invention allows the user to specify a certain voltage level, and the user-specified input voltage is then compared by a voltage comparison circuit to determine which voltage range the user-specified input voltage lies to thereby generate an output logic signal whose value corresponds to the desired option. This multi-option setting device allows the user to select from more than two options, while nevertheless allowing the overall system to operate normally without being affected by the setting.